This invention relates to a camshaft supporting structure for a four-stroke cycle engine and more particularly to an improved camshaft mounting and driving arrangement for such engines that permits a compact engine construction.
In conjunction with internal combustion engines and particularly those utilized for automotive vehicle application, there is an increasing pressure on the designer to make the engine more compact. Engine compartments in modern vehicles are becoming much smaller and the hood line is also kept low in order to improve aerodynamics. This substantially reduces the space available for the engine. However, there is also a demand for high output engines and this generally requires a resort to multiple cylinders.
In connection with modern automotive practice, the engine is often mounted transversely in the engine compartment. Although V-type engines permit a compact engine construction, they do not lend themselves to transverse engine placement particularly where they are high output type engines such as those having double overhead camshafts. One reason why double overhead-camshaft engines presents a problem in transverse engine placement is that the camshafts and their drives take up considerable space and thus, it is difficult to place a V-type engine in this kind of an orientation.
It is, therefore, a principal object to this invention to provide an improved mounting and driving structure for a twin overhead camshaft engine and more particularly one wherein the cylinder block is inclined from the vertical as in a V-type engine.
It is a further object to this invention to provide an improved and compact engine arrangement for a double overhead cam engine suitable for automotive application.
A first feature of the invention is adapted to be embodied in a cylinder head arrangement for a twin overhead camshaft internal combustion engine. The cylinder head has a lower surface that is adapted to be positioned in confronting relationship to the cylinder bore of a cylinder block. The lower surface cooperates with the cylinder bore and a piston reciprocating therein to form a combustion chamber. A pair of camshafts are journalled for rotation in the cylinder head about camshaft axes that extend parallel to the rotational axis of a crankshaft driven by the piston associated with the cylinder bore. The camshaft axes are disposed on opposite sides of a plane containing the axis of rotation of the associated crankshaft and the axis of the associated cylinder bore. The distance between the cylinder head lower surface and one of the camshaft axes is substantially less than the distance between the cylinder head lower surface and the other of the camshaft axes.
Another feature of the invention is adapted to be embodied in an internal combustion engine for positioning in an engine compartment of the vehicle for powering the vehicle. The engine compartment is defined at least in part by a wall of the vehicle body. The engine comprises a cylinder block defining at least one cylinder bore. A piston reciprocates in the cylinder bore and drives a crankshaft journalled for rotation about a crankshaft axis at a lower end of the cylinder block. The cylinder block is inclined so that the cylinder bore extends upwardly from the crankshaft axis toward the vehicle wall. A cylinder head having lower surfaces positioned in confronting relationship to the cylinder bore and encloses the cylinder bore. The lower surface cooperates with the cylinder bore and the piston to form a combustion chamber. A pair of camshafts are journalled for rotation in the cylinder head about camshaft axes that are parallel to the crankshaft axis. The camshafts axes are disposed on opposite sides of the plane containing the crankshaft axis and the cylinder bore. The distance between the cylinder head lower surface and the camshaft axis closest to the vehicle wall is substantially less than the distance between the cylinder head lower surface and the other of the camshaft axes.
In accordance with another feature of the invention which can be utilized with a cylinder head or an internal combustion engine as set forth in the preceding two paragraphs, the camshaft that is disposed furthest from the crankshaft axis is driven directly from the crankshaft and the other camshaft is driven from the crankshaft driven camshaft.